1. Field of the Invention
The present invention relates to a failure check apparatus which is applied to a control apparatus that is mounted on the body of a vehicle and that includes a plurality of types of actuators, such as an antilock brake system, and which activates the plurality of types of actuators in a failure check pattern to thereby perform failure check of the control apparatus.
2. Description of the Related Art
Heretofore, an antilock brake system (hereinafter may be referred to as “ABS” for preventing lock of wheels during travel of a vehicle has been widely provided on vehicles. In such an antilock brake system, in general, a motor for driving a hydraulic pump, a plurality of solenoid valves, and the like (that is, plurality of types of actuators) disposed in the system are activated in a predetermined pattern within a predetermined short period after startup of an engine (that is, after startup of the system) so as to perform failure check of the system (specifically, check for wire breakage, short circuit, etc.).
Since such failure check is typically performed before a vehicle begins travel; i.e., during a period in which noise from the engine is of a relatively low level and no road noise is generated, an operation sound generated upon activation of actuators such as solenoid valves and a motor is likely to be transmitted to the ears of an occupant of the vehicle as a sound harsh to the ears, whereby the occupant experiences an unpleasant sensation.
In order to cope with such a problem, a failure diagnostic apparatus for an ABS disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. S63-71468 performs ABS failure diagnosis (failure check) under the condition that the acceleration of a vehicle body or wheels is equal to or higher than a predetermined level. Further, a brake control apparatus disclosed in, for example, Japanese Patent Application Laid-Open (kokai) No. H10-24826 performs ABS failure check under the condition that the speed of a vehicle body is equal to or higher than a predetermined level. In these apparatuses, since ABS failure check is performed when noise that is unavoidably transmitted to a vehicle occupant, such as engine noise and road noise, is of a relatively high level, the occupant hardly senses, as a sound harsh to the ears, an operation sound of solenoid valves, a motor, etc. generated during the failure check. As result, the unpleasant sensation given to the occupant by the operation sound can be mitigated.
However, in the apparatuses disclosed in the above-described publications, ABS failure check is executed after a vehicle has actually begun travel. From the viewpoint of early discovery of failure, such failure check is desired to be performed before the vehicle begins travel. In view of this, the present inventors has studied methods for mitigating unpleasant sensation given to a vehicle occupant by the above-mentioned operation sound even when the magnitude of noise transmitted to the vehicle occupant is of relatively low level, such as before the vehicle begins travel. As a result, the present inventors has found a method for mitigating unpleasant sensation given to a vehicle occupant by the above-mentioned operation sound, by means of improving the sound quality of the operation sound transmitted to the ears of the vehicle occupant.